Periodic glitches - problems with our Blackmagic hyperdeck

We're looping a ProRes422 UHD file from a Blackmagic hyperdeck, but we are experiencing some periodic glitches in the image every 2 - 3 hours (see image below). We've been troubleshooting the past couple of days, but have had no luck isolating the problem. What else should we be considering?

The software on the Blackmagic Deck is up to date.
We assume the file is fine, as we aren’t experiencing the glitches every time (it’s a 20 minute video) and it seems as if the audio is unaffected.
We've switched out the HDMI cable, but no luck.